Damper assemblies generally comprise a damper frame, usually of rectangular configuration, within which are pivotally mounted a plurality of damper blades, also usually rectangular, these blades pivoting between a closed position in which they lie in a plane extending across the opening in the frame to block the same, and an open position in which the blades are at an angle to the plane of the frame opening. The blades are interconnected by a linkage so that pivotal movement of one blade is transmitted to the other blades to cause all of the blades to pivot together. In this combined pivotal movement, all of the blades may remain in parallel planes, or they may rotate oppositely.
Prior multi-blade damper assemblies have required precision construction, they have tended to bind, and all of the blades have had to be of the same size. These problems are more fully described, together with a partial solution to the problem, in U.S. Pat. No. 3,267,962 issued to myself and Ho Chow on Aug. 23, 1966.
In the invention of U.S. Pat. No. 3,267,962, brackets are mounted on each of the blades, these brackets having an elongated portion which extends outwardly beyond an end of the blade. Centrally positioned blades are provided with a pair of shanks extending transversely in opposite directions from the elongated portion of the bracket. These shanks are swivelly disposed with respect to the bracket to be rotatable on their own axis. Rods are then connected to these shanks to interconnect the centrally positioned blades with blades on both sides thereof. This eliminates the need for precision alignment of the blades and of the brackets on the blades, and the chance of binding is minimized.
The assemblies needed in U.S. Pat. No. 3,267,962 are complex and involve the assembly of many parts as described in the patent. Moreover, in order to equip a multiblade damper for operation, three different brackets are required. One bracket assembly has the swivelly mounted shank on the left side, one has the swivelly mounted shank on the right side, and a third has the swivelly mounted shank on both sides. These complexities add significantly to the cost of construction and they make the assembly task more difficult.